1. Field of the Invention
This invention relates to a data recording and/or reproducing apparatus and, more particularly, to a data recording and/or reproducing apparatus used with advantage for recording, reproducing or editing of video and audio data.
2. Description of the Related Art
Recently, with diversification of information furnishing channels, brought about by the coming into widespread use of cable television (CATV), there is raised an increasing demand for recording plural sorts of video and audio data simultaneously from a sole audio video data recording and/or reproducing apparatus or reproducing the data as it records the data. In order to meet this demand, there is coming into widespread use an apparatus termed a video server or an AV (audio and/or video) server, and which records and/or reproduces the image and the speech using a random-accessible recording medium, such as a hard disc.
In general, the video server in a broadcasting station needs to be of high data transfer rate, in view of a demand for high image and speech quality, and of large capacity in order to be able to record data continuing for prolonged time. For satisfying this demand, a data recording and/or reproducing apparatus including plural hard disc (HD) devices capable of storing image and speech data and of parallel processing is used in an attempt to speed up the data transfer rate and to increase the storage capacity as well as to keep parity data recorded in order to assure reliability in case of possible failure of one of the HD devices. By shifting the playback time of the same material data to reproduce the data on multiple channels, it is possible to implement a multi-channel video server capable of accommodating multifarious use configurations, such as by constructing a video-on-demand (VOD) or near-video-on-demand (NVOD).
In the data recording and/or reproducing apparatus, used for such video server, there is employed a technique of Redundant Arrays of Inexpensive Discs (RAID) employing plural HDs as proposed in a treatise in ACM SIGMOND Conference, Chicago, Ill., Jun. 13, 1988, by Patterson et al., entitled “A Case for Redundant Arrays of Inexpensive Discs (RAID)” issued in 1988, in which plural hard disc drives, each made up of plural HDs, are used.
In the above treatise, the RAID is classified into RAID-1 to RAID-5. The RAID-3 splits the input data into pre-set lengths recorded in plural HDDs and generates parity data, which is an EX-OR output of associated data blocks of each HDD, to write the parity data in the other HDD. The RAID-5 is such a system in which the data dividing unit (block) is increased to record the divided block as a data block in a HDD, while the EX-OR output of the associated data blocks of each HDD (parity data) is recorded as a parity block in the other HDD, with the parity block being distributed in other HDDs.
For other RAIDs, reference is had to the above treatise.
Meanwhile, the material actually used in a news program or a sports program is sent out after processing such as editing in the broadcasting station. Since emergency materials need to be transmitted in a news program, and sports programs are occasionally extended in the broadcast time, it is desirable to reduce the editing time.
For carrying out this editing operation, the routine practice is to connect the editing device to the VTR, to decide the material to be transmitted, as the reproduced material on the VTR is checked on an editing device, to record the material on a recording VTR and to transmit the recorded tape from the transmitting VTR.
For shortening the editing time, there is recently used an editing configuration termed a non-linear editing. There is, for example, such a configuration in which the aforementioned AV server is connected to the editing device, the material stored in the AV server is reproduced, the material to be transmitted is decided in the editing device and the material stored in the AV server is transmitted from the editing point information, also termed an editing decision list (EDL). In this case, the time for material search is short, in distinction from the conventional linear editing, such as VTR, such that the material recorded with time lead or time lag can be located or reproduced freely.
However, the editing device needs to be provided in addition to the AV servers even in the non-linear editing configuration, thus taking up the dedicated space. This problem is felt more keenly in case of a relay car having only a limited space. Similarly, a special effect device needs to be mounted if a special effect is to be achieved.
Also, there are not many experienced editors in the non-linear editing. In actual broadcasting stations, linear editing for a tape recording medium is performed in an actual broadcasting station such that many editors are accustomed to this editing configuration.
Moreover, if non-linear editing is to be performed on both the AV server and in the editing device, there are occasions wherein instantaneous cut editing cannot be performed because of the time-divisional control for the storage medium of the AV server, even in case of simple cut editing. That is, the AV server has plural channels, that is plural inputs/outputs, and each channel is adapted to time-divisionally access the HDD in order to make arbitration in using the HDD as the recording medium, or in order to make arbitration in using an internal bus connected to the HDD. By this time-divisional control, there is produced a slight time loss until the material is reproduced responsive to a command from the editing device. This presumably is responsible for the extraneous feeling on the part of the audience to the operation by the editing personnel.